Xantia td engine K light keeps popping on

[Timmo]

Evening guys, recently in the veg burner the engine k light flickers on when idling, engine warm, tickle the throttle and it goes out, pops on randomly, first noticed it when in france, had issues with the battery, changed for new, wondering if i disturbed anything likely to trigger the light?
When checking what was giving issues i noticed that the starter main cable had loosened, checked and re attached that, replaced the earth terminal as that had split, then battery as despite the green indicator on it, it wouldn't give enough power to activate the electrical bits, instead sending the dials intl a frenzy of sweeping and the various relays clicking away.
The car has been spot on either side of the battery issue, cruising effortlessly both sides of the channel, the light pops on only when on idle, no loss of power, a raise in the revs of 100rpm turns it out, i don't want to ignore it if there is a possible reason for it?
Any pointers for where to start looking?

[CitroJim]

This is often caused by low fuel pressure Dom, and that causes the timing to vary out of control...

Replace your fuel filter and check your tank strainer is clear...

If it only comes on on the over-run don't worry - mine does that occasionally...

[Timmo]

Thanks Jim, fuel filter was new week before we went to france, but hardly cost the earth to replace. Will grab a spare and chuck it in, will pull the strainer out as tank is quite low on fuel at the mo,

[CitroJim]

If you have a Lexia Dom, check for any stored faults; if there are I'd almost put money on it being a timing fault..

May also be caused by the Needle Lift Sensor... Check its connector and its continuity... If memory serves it should show a resistance of around 100 ohms... The connector can become contaminated and shake apart under engine vibration...

[MikeT]

Oooh, this is interesting (for me)! As Jim says, the engine light can betray a fuel flow restriction, which can throw the timing advance out of whack, hence the warning light.
However IIRC, this usually manifests at higher rpm/fuel flow, whereas yours is only happening at low rpm/fuel flow and clears as the rpms/fuel flow increase.#

Definitely follow Jim's advice and eliminate the fuel supply system but I'm wondering if it could be the pump showing it's age also. Let us know how you get on.

#The diesel pump, unlike modern common rail systems, is internally both the low-pressure "lift pump" and "high-pressure injection pump". It is the former part that creates the required pressure for the timing advance module to work from, as well as drawing the fuel through from the tank, the fuel lines and fuel filter.

This is achieved by spinning 4x free-sliding "vanes" in an elliptical orbit to paddle the fuel, creating the desired pressure. If these vanes stick or are worn, the required pressure may not be achieved, especially at very low rpm.
Equally, (though not likely the cause in your case) there is a spring-loaded pressure regulator that will open and relieve any excess pressure (as the pump spins faster with higher rpms), keeping the pressure constant. If this device is worn or gummed, it too will affect the factory-set pressure.

[Timmo]

No lexia Jim, (btw. Who's Dom?? ) not sure of anyone down here with one??
Will check the sender bit, - retaining ring normally threaded or reverse? I can't remember from when i had it out last! ( last year i think)
Will check the pump area and wiring for any obvious reasons, just struck me as odd that it started after the battery issue

[CitroJim]

btw. Who's Dom??

Sorry Timmo, I was getting confused... Easy at my age

Won't happen again..

Mike is right that wear in either the vane pump or the timing device actuator piston could well cause this..

Tell me, when the fault is apparent does the engine note change appreciably? Do you hear a definite increase or decrease in diesel knock, especially at idle...

[Timmo]

Not that ihave noticed, just lights up, will keep an eye on it or an ear as such, due to remarkably heavy downpours i am decluttering the desk rather than fighting the car!

[MikeT]

I'd also be interested to know if recharging the tank stops the engine light illuminating at idle. The slight increase in "head pressure" from the fuel in the tank may well be enough to mask the weakness, as you say it's currently very low on fuel.

[CitroJim]

I'd also be interested to know if recharging the tank stops the engine light illuminating at idle. The slight increase in "head pressure" from the fuel in the tank may well be enough to mask the weakness, as you say it's currently very low on fuel.

That's a very good point... You're thinking very well today Mike

[MikeT]

I'd also be interested to know if recharging the tank stops the engine light illuminating at idle. The slight increase in "head pressure" from the fuel in the tank may well be enough to mask the weakness, as you say it's currently very low on fuel.

That's a very good point... You're thinking very well today Mike

I missed the possibility of the timing advance being sticky, which you caught nicely, Jim! But thanks for the compliment, it re-inforces the fact I'm still only in the "early-onset stage" (of dementia or alka-seltzer).

[CitroJim]

But thanks for the compliment, it re-inforces the fact I'm still only in the "early-onset stage" (of dementia or alka-seltzer).

That's good Mike Pleased to be of service

It helps me know I'm OK too as reinforced today when I sorted some 200 parkrun finish tokens into numerical order

[myglaren]

I had to do a load of cognitive testing yesterday.



I think I failed and they will be coming foe me soon.

[Timmo]

Popped out earlier with the eldest daughter venturing intk Camborne (yes, i Did go up Camborne hill Incase your into the old pub sing along days of 'Going up Camborne hil coming down....), the light flickered on when we were in traffic, no notable change in engine tone, went out before i could flick the throttle, didn't come on again for the trip, chucked 10L derv in it as a treat as for the french run (last month on the 20th when last filled up) it was running on 15L derv and 50L fresh veg, had done 550 miles, but a fair amount of idling to check it would start then leave going to not kill the new battery off, not the best mpg ive had, but pretty average, i first noticed it when it had 3/4 tank of fuel as we rolled off the ferry this side.
I'll have a look at it tomorrow and see if anything obvious,

[Timmo]

Okay guys, small video of the light fro. Today, quick trip to tesco, as pulled into a space and idled up it popped,

Sound is there but was from inside the car,